Described herein is a process for the fabrication of an electronic device. More specifically, described herein are compositions for forming a silicon-containing film in a deposition process, such as, for example, a flowable chemical vapor deposition. Exemplary silicon-containing films that can be deposited using the compositions and methods described herein include silicon oxide, silicon nitride, silicon oxynitride or carbon-doped silicon oxide or carbon-doped silicon nitride films.
Flowable oxide deposition methods typically use alkoxysilane compounds as precursors for silicon-containing films which are deposited by controlled hydrolysis and condensation reactions. Such films can be deposited onto a substrate, for example, by applying a mixture of water and alkoxysilanes, optionally with solvent and/or other additives such as surfactants and porogens, onto a substrate. Typical methods for the application of these mixtures include spin coating, dip coating, spray coating, screen printing, co-condensation, and ink jet printing. After application to the substrate and upon application of one or more energy sources such as, for example, thermal, plasma, and/or other sources, the water within the mixture can react with the alkoxysilanes to hydrolyze the alkoxide and/or aryloxide groups and generate silanol species, which further condense with other hydrolyzed molecules and form an oligomeric or network structure.
Besides physical deposition or application of the precursor to the substrate, vapor deposition processes using water and a silicon containing vapor source for flowable dielectric deposition (FCVD) have been described, for instance, in U.S. Pat. Nos. 7,541,297; 8,449,942; 8,629,067; 8,741,788; 8,481,403; 8,580,697; 8,685,867; 7,498,273; 7,074,690; 7,582,555; 7,888,233, and 7,915,131, as well as U.S. Publ. No. 2013/0230987 A1, the disclosures of which are incorporated herein by reference. Typical methods generally relate to filling gaps on substrates with a solid dielectric material by forming a flowable liquid film in the gap. The flowable film is formed by reacting a dielectric precursor which may have a Si—C bond with an oxidant to form the dielectric material. In certain embodiments, the dielectric precursor condenses and subsequently reacts with the oxidant to form dielectric material. In certain embodiments, vapor phase reactants react to form a condensed flowable film. Since the Si—C bond is relatively inert towards reaction with water, the resultant network may be beneficially functionalized with organic functional groups which impart desired chemical and physical properties to the resultant film. For example, the addition of carbon to the network may lower the dielectric constant of the resultant film.
Another approach to depositing a silicon oxide film using flowable chemical vapor deposition process is gas phase polymerization. For example, the prior art has focused on using compounds such as trisilylamine (TSA) to deposit Si, H, N containing oligomers that are subsequently oxidized to SiOx films using ozone exposure. Examples of such approaches include: U.S. Publ. No. 2014/0073144; U. S. Publ. No. 2013/230987; U.S. Pat. Nos. 7,521,378, 7,557,420, and 8,575,040; and 7,825,040, the disclosures of which are incorporated herein by reference.
Regarding the processes that employ trisilylamine (TSA), TSA is typically delivered into the reaction chamber as a gas, mixed with ammonia, and activated in a remote plasma reactor to generate NH2, NH, H and or N radicals or ions. The TSA reacts with the plasma activated ammonia and begins to oligomerize to form higher molecular weight TSA dimers and trimers or other species which contain Si, N and H. The substrate is placed in the reactor and cooled to one or more temperatures ranging from about 0 to about 50° C. at a certain chamber pressures and TSA/activated ammonia mixtures the oligomers begin to condense on the wafers surface in such a way that they can “flow” to fill the trench surface feature. In this way, a material which contains Si, N and H is deposited onto the wafer and fills the trench. In certain embodiments, a pre-anneal step is performed to allow the film to be more SiN-like. It is desirable to have a SiN material because the next process step is oxidation at one or more temperatures ranging from 100-700° C. using ozone or water. Because of the SiN bond distance and angles, it is known that as SiN is oxidized to SiO2 there is a unit cell volume increase which prevents the film from shrinking.
Despite the recent activity in the art related to flowable chemical vapor deposition and other film deposition processes, problems still remain. One of these problems is related to film composition. For example, flowable oxide films deposited from the precursor trisilylamine (TSA) in a gas phase polymerization process yield films with a high density of Si—H bonds and have a wet etch rates in dilute HF solutions that are 2.2 to 2.5 times faster than high quality thermal oxide. Such films are not suitable for low-k film applications.
In many circumstances, a hardening process, including thermal annealing, UV cure, or ion/radical densification, may be applied to the flowable films. The hardening process may remove carbon groups, hydroxyl groups and smaller molecular weight species from the deposited materials. Referring now to FIG. 1, this often leaves voids, cracks or spaces in the hardened material. Such films are also not suitable for low-k film applications.
Thus, there is a need to provide alternative precursor compounds to produce silicon-containing films via flow CVD techniques that have the mechanical integrity and porosity to successfully function as low-k silicon oxide containing film material.